There is known a traditional refrigeration cycle apparatus that includes a compressor having an orbiting scroll which is driven by a motor and is configured to compress a refrigerant, a radiator which dissipates heat of the refrigerant compressed by the compressor, an expander having a rolling piston which is configured to decompress the refrigerant that has passed through the radiator, and an evaporator which allows the refrigerant decompressed by the expander to evaporate. Such a refrigeration cycle apparatus has been known which has a communicating path connecting an intermediate position of the expansion process in an expansion chamber (a section partitioned by the rolling piston in the expansion chamber) to an outlet position (outlet port side) such that when a pressure in the expansion chamber excessively drops, fluid on the outlet side is returned to the expansion chamber in order to prevent overexpansion and thus prevents a drop in power recovery efficiency (refer to, for example, Patent Literature 1).
In addition, a refrigerating and air-conditioning apparatus is known that includes a scroll expander, which expands and decompresses a refrigerant cooled by a radiator to recover power, and a scroll auxiliary compressor, which is driven by power recovered by the expander and compresses the refrigerant in an auxiliary manner. With the auxiliary compression of the refrigerant by the auxiliary compressor, load on a main compressor is reduced, the electric power necessary for a drive motor of the main compressor is reduced, and, thus, efficiency of the refrigeration cycle apparatus is increased (refer to, for example, Patent Literature 2).